Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752727AbdC0Mci (ORCPT ); Mon, 27 Mar 2017 08:32:38 -0400 Received: from mail-pg0-f67.google.com ([74.125.83.67]:35637 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752176AbdC0Mcc (ORCPT ); Mon, 27 Mar 2017 08:32:32 -0400 Reply-To: minyard@acm.org Subject: Re: [PATCH v2] ipmi: Fix kernel panic at ipmi_ssif_thread() References: <1490599902-45215-1-git-send-email-joechang@qti.qualcomm.com> To: Joeseph Chang , joechang@codeaurora.org, openipmi-developer@lists.sourceforge.net, linux-kernel@vger.kernel.org Cc: anjiandi@codeaurora.org From: Corey Minyard Message-ID: Date: Mon, 27 Mar 2017 07:32:02 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <1490599902-45215-1-git-send-email-joechang@qti.qualcomm.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3218 Lines: 93 On 03/27/2017 02:31 AM, Joeseph Chang wrote: > From: Joeseph Chang > > Since patch v1 touch ssif_info->multi_pos and ssif_info->multi_data > after ssif_i2c_send(). msg_written_handler can be called at any time > after ssif_i2c_send(). There is possible to have concurrent access to > ssif_info->multi_pos or ssif_info->multi_data at msg_written_handler. > > Revert patch v1 and add new local pointer "i2c_data" which point to > i2c data and size that will be sent out to avoid concurrent access in > msg_written_handler(). > > Signed-off-by: Joeseph Chang > --- > drivers/char/ipmi/ipmi_ssif.c | 24 ++++++++++++------------ > 1 file changed, 12 insertions(+), 12 deletions(-) > > diff --git a/drivers/char/ipmi/ipmi_ssif.c b/drivers/char/ipmi/ipmi_ssif.c > index 39346ee..f36f018 100644 > --- a/drivers/char/ipmi/ipmi_ssif.c > +++ b/drivers/char/ipmi/ipmi_ssif.c > @@ -852,6 +852,7 @@ static void msg_written_handler(struct ssif_info *ssif_info, int result, > unsigned char *data, unsigned int len) > { > int rv; > + unsigned char *i2c_data; The variable should be in the block where it is used. The basic rule is to limit scope as much as possible. The name is also a little vague, though not terrible. > > /* We are single-threaded here, so no need for a lock. */ > if (result < 0) { > @@ -899,13 +900,22 @@ static void msg_written_handler(struct ssif_info *ssif_info, int result, > left = 32; > /* Length byte. */ > ssif_info->multi_data[ssif_info->multi_pos] = left; > + i2c_data = ssif_info->multi_data + ssif_info->multi_pos; > + ssif_info->multi_pos += left; > + if (left < 32) > + /* > + * Write is finished. Note that we must end > + * with a write of less than 32 bytes to > + * complete the transaction, even if it is > + * zero bytes. > + */ > + ssif_info->multi_data = NULL; Can you make this change not relative to the previous change? Just do a "git rebase -i ...." and squash the changes. I saw your previous emails, but I can't take those because of the comments at the top and the text from the reply. You can add comments to a submission that don't go into git, just put them after the '---" in the header. Thanks, -corey > > rv = ssif_i2c_send(ssif_info, msg_written_handler, > I2C_SMBUS_WRITE, > SSIF_IPMI_MULTI_PART_REQUEST_MIDDLE, > - ssif_info->multi_data + ssif_info->multi_pos, > + i2c_data, > I2C_SMBUS_BLOCK_DATA); > - > if (rv < 0) { > /* request failed, just return the error. */ > ssif_inc_stat(ssif_info, send_errors); > @@ -914,16 +924,6 @@ static void msg_written_handler(struct ssif_info *ssif_info, int result, > pr_info("Error from i2c_non_blocking_op(3)\n"); > msg_done_handler(ssif_info, -EIO, NULL, 0); > } > - > - ssif_info->multi_pos += left; > - if (left < 32) > - /* > - * Write is finished. Note that we must end > - * with a write of less than 32 bytes to > - * complete the transaction, even if it is > - * zero bytes. > - */ > - ssif_info->multi_data = NULL; > } else { > /* Ready to request the result. */ > unsigned long oflags, *flags;